Granulating apparatus

ABSTRACT

A substantially horizontally disposed drum is supported for rotation. One end of the drum is adapted to receive lumps of material which are granulated within the drum by abrasive particles which are projected from an abrasive throwing wheel. The drum includes a plurality of apertures through which the granulated material and abrasive particles are removed and subsequently conveyed to a separator for separating the granulated material from the abrasive particles. The apparatus may include a conditioner which scours the granulated material.

United States Patent 1191 Carpenter, Jr. et a1.

145 Nov. 19, 1974 1 GRANULATING APPARATUS [75] Inventors: James H.Carpenter, Jr.; Bernard W. lxer, Hagerstown, Md.

[73] Assignee: The Carborundum Company,

Niagara Falls, N.Y.

22 Filed: May 17, 1972 21 Appl. No.: 254,279

2,942,731 6/1960 Soldini 241/91 UX 3,585,758 6/1971 Harper 51/133,693,296 9/1972 Carpenter.... 51/9 X 3,716,947 2/1973 Carpenter....51/9 3,750,339 8/1973 Barnes 51/9 FOREIGN PATENTS OR APPLICATIONS454,662 6/1968 Switzerland 51/9 1,093,785 12/1967 Great Britain 51/13Primary Examiner-Donald G. Kelly Attorney, Agent, or Firm-David E.Dougherty 7] ABSTRACT A substantially horizontally disposed drum issupported for rotation. One end ofthe drum is adapted to receive lumpsof material which are granulated within [56] References Cited the drumby abrasive particles which are projected UNITED STATES PATENTS from anabrasive throwing wheel. The drum includes a 762,596 6/1904 Packer 241010. 10 plurallty of apemlres Waugh whlch the granulated 2,211,0998/1940 Coffey 51/13 mateflal and abraslve PartlcleS are removed and2,261,947 11/1941 Bamebel 24 10 sequently conveyed to a separator forseparating the 2,441,578 5/1948 Keefer... 51/13 granulated material fromthe abrasive particles. The 2,478,461 8/1949 Connolly.. 241/D1G. 1Oapparatus may include a conditioner which scours the 2,696,910 12/1954Ljungdell 51/14 X granulated material, 2,707,314 5/1955 Horth 24l/DIG.10 2,834,553 5/1958 Neely 241/91 3 Claims, 12 Drawing Figures 1 l l H 535 PATENTEL HEY I 9 I974 SHEET 2 0F PATENIEL W I IB" 3 848,81 5

saw .3 OF 6 PATENTEL W 1 3.848.815

SHEET 5 OF 6 y w F4 77.

GRANULATING APPARATUS BACKGROUND OF THE INVENTION The present inventionrelates to an apparatus for granulating lumps of material, especiallylumps of molded sand.

Reconditioning of used sand from a shake-out operation involves reducingused core elements and molded sand lumps to individual sand grains andremoving the metallic particles, sintered clusters of sand grains,excess fines and other tramp and objectionable material. The quality ofreclaimed sand must be comparable to that of new sand so that it may besatisfactorily substituted for new sand in sand mixtures withoutappreciable change in sand practice.

Foundries are adopting a practice utilizing quality sand, a chemicalbinder, and a catalyst which are mixed together and hardened into asolid cake at ambient temperatures to form a chemically bonded mold.Since baking is not required, this process is known in the art asno-bake molding. The no-bake molding process has distinct advantagessuch as ease of making a mold, cleaner environment, ease of handling acompleted mold, and improved casting finishes and casting tolerances.

Despite the numerous advantages, there are a number of disadvantages,such as the increased cost for quality grade sand. Therefore, theeffective and efficient reclamation of sand can play a significant partin making the no-bake molding process economically attractive. One ofthe steps in the reclamation of sand used in no-bake molding is thereduction of lumps of molded no-bake sand.

Prior art apparatus typically used for granulating lumpy materialinclude hammermills, ring crushers, jaw or roll crushers which generallysubject moving parts to excessive wear and stresses thereby decreasingmachine life and increasing machine breakdowns. The large quantity ofdust created by prior art apparatus is not only an undesirable pollutantbut is evidence that the lumps are crushed to such an extent that a goodyield of granulated material such as reclaimed sand is sacrificed.

SUMMARY OF THE INVENTION In an apparatus for granulating lumps, a drumhaving a plurality of apertures for the passage of granulated materialand abrasive particles is supported for rotation about a substantiallyhorizontal axis. The drum includes a spiral screw connected to the innersurface. Rotation of the drum causes the lumps to move toward a streamof abrasive particles projected with sufficient force to granulate thelumps. A separator removes the granulated material from the spentabrasive particles.

The present invention obviates one or more deficiencies of prior artdevices and efficiently and effectively reclaims sand from lumps ofmolded sand.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational viewschematically showing one embodiment of the present invention;

FIG. 2 is an end elevational view of the embodiment shown in FIG. 1;

FIG. 3 is a cross-sectional view through FIG. 2 along the line 3-3;

FIG. 4 is an end view of the apparatus of FIG. 3;

FIG. 5 is a side elevational view in section of one embodiment of thedrum;

FIG. 6 is a side elevational view in section of another embodiment ofthe drum;

FIG. 7 is an end elevational view of the drum shown in FIG. 6;

FIG. 8 is a side elevational view in section of the conditioner;

FIG. 9 is a side elevational view shown in section of the centrifugalthrowing wheel of the conditioner;

FIG. 10 is a top view of the centrifugal throwing wheel of FIG. 9;

FIG. 1 l is a side elevational view schematically showing a sandconditioning system of the present invention; and

FIG. 12 shows an end elevational view of a sand reclamation system witha sand conditioning system connected thereto.

DETAILED DESCRIPTION Although the detailed description of the presentinvention is directed to the reclamation of sand from lumps of moldedsand, it should be realized that the apparatus and process of thisinvention can be conveniently used to pulverize or reduce the size oflumps of various materials other than sand lumps, such as coal,phosphate rock, lime, rock salt, cement clinker, coke and various othermaterials.

Referring to the drawings in more detail, a feed mixture 11 whichincludes lumps of molded sand, and may include core rods, hangers, trampiron of various sizes, sweepings and spillage, is fed through the feedtube 13 to an oscillating conveyor 15.

One method of forming the feed mixture comprises projecting abrasiveparticles against a mold with the casting therein to remove the sand androds from the casting and cleaning the exposed casting in one operation.This is accomplished in a blast chamber with the sand, rods, spentabrasive, fines and other contaminants falling through the bottom of thechamber from where it is conveyed into the feed tube 13 and onto anoscillating conveyor 15.

The oscillating conveyor 15 includes a screen 17 of appropriate meshsize to permit the fines and small particles to fall into a hopper 19and thence to an oscillating conveyor 21. The molded sand lumps, corerods,

and any other elements in the mixture 11 which have a size larger thanthe apertures in the screen 17 are fed by the oscillating conveyor 15into one end of a barrel or drum 25 which is mounted for rotation abouta substantially horizontal axis.

The drum 25 is mounted for rotation between a pair of shafts 27 whichare generally parallel to the axis of rotation of the drum 25. Theshafts 27 have a plurality of rollers 29 mounted thereon in drivingengagement with the drum 25. The shafts 27 are driven by a suitablemotor 31. During rotation of the drum 25, abrasive particles aresupplied to an abrasive blast means 33 from a feed hopper 35. Theabrasive particles are projected into the lumps of molded sand withinthe drum 25 thereby granulating the sand into fine particles.

The interior surface of the drum 25 is provided with a spiral screw 37which drives the feed mixture 11 from an inlet end toward an outlet end38. As illustrated in FIG. 3, the screw 37 comprises a plurality ofsections or flights which extend over the entire interior surface of thedrum 25. A flight is a portion of the spiral screw 37. The flightsadjacent the inlet end project into the drum a greater distance thanthose near the outlet end 38. Preferably the projection of the flightstapers uniformly from a maximum of about 6 inches to the inlet end ofthe drum 25 to a minimum projection of about Va inch at the exit oroutlet end 38 of the drum 25. As abrasive particles are projected intothe drum 25 from the outlet end 38, the lumps of molded sand are forcedagainst the flights by the force of the abrasive shot. This force causesthe large lumps to roll back over the short flights at the outlet end 38and back into the drum 25. Thus, the larger lumps tend to remain in thebarrel for a longer length of time which is necessary to effect a propersize reduction.

The drum 25 is provided with a plurality of apertures 39 to permit thepassage of abrasive particles and granulated sand onto the oscillatingconveyor 21 positioned below the drum 25. The abrasive particles andgranulated sand pass through the upper surface 41- of the oscillatingconveyor 21 and are conveyed along the bottom of the conveyor 21 to exitvia passage 43. The core rods, trash and elements larger than theapertures 39 are driven by the spiral screw 37 out the outlet end 38 ofthe drum 25 and onto the upper surface 41. These larger elements remainon the screen deck or upper surface 41 of the oscillating conveyor 21and are discharged therefrom.

FIGS. 5, 6 and 7 illustrate preferred embodiments of the drum 25 of thepresent invention. In FIG. 5, a preferred embodiment of the spiral screw37 is illustrated. In this case, the spiral screw 37 terminatesintermediate the ends of the drum 25, preferably about in the middle ofthe drum 25. This arrangement is preferable when the feed mixturecomprises substantially lumps of molded sand. Due to the absence offlights at outlet end 38 of the drum 25, the force of the projectedabrasive particles tends to keep the lumps within the drum 25 until theyare completely granulated. If the feed mixture 11 contains core rods andother material which must be conveyed out the outlet end of the drum 25,it is preferable to have flights extending to the outlet end 38.

FIGS. 6 and 7 illustrate a preferred embodiment of the drum 25 of thepresent invention when the feed mixture 11 contains rods. In this case,the spiral screw 37 extends throughout the entire length of the drum 25.The rod 45 which is parallel to the axis of rotation of the drum 25 isspaced from the inside surface of the drum 25 so as to block the upwardmovement of core rods as the drum 25 rotates. Thus, core rods areprevented from tumbling and being blasted into the interior of the drum25 by the force of projected abrasive particles. A spring loaded bracket47 holds the rod in the proper position. Each bracket 47 is rigidlymounted at one end to the rod 45 and pivotably mounted at the other endfor movement about a fixed axis 49. This pivotable mounting preventscore rods from becoming wedged between the rod 45 and the interiorsurface of the drum 25.

The abrasive blast means 33 includes a motor with a throwing wheel 51mounted directly on the motor shaft. The throwing wheel 51 includes arunnerhead having a plurality of throwing vanes radially mountedthereon. The throwing wheel 51 is positioned at the outlet end 38 of thedrum 25 and exterior thereto. The

throwing wheel 51 is disposed at an angle to the axis of rotation of thedrum 25 so that the abrasive particles or shot strike the tumbled pileof molded sand lumps from the lower end of the pile to the higher endthereof. The shot which is preferably large size metal shot iscontinuously projected into the mixture within the drum 25. The blastingstream is propelled lengthwise of the drum 25 for substantially the fulllength and contacts with blasting velocity the lumps of sand therein.The arrangement is such that the effect of the blast stream is to drivethe lumps of molded sand against the direction of flow imparted by thespiral screw 37. The spiral screw 37 acts as a stop to prevent thebackward flow and holds the lumps of molded sand against the force ofthe stream of shot until the lumps are effectively granulated. The drum25 is mounted within an enclosed cabinet 53. A plurality of flexiblevertically extending skirts 55 hang from the cabinet 53 to prevent theloss of ricocheting shot.

The sand and shot mixture passes through passage 43 into a conditioner57. The conditioner 57 subjects the sand in the mixture to a scouringtreatment thereby removing accumulated coatings. After scouring, thesand is conveyed by an elevator 59 into an air wash separator 61 whichseparates the sand from the shot. Although FIGS. 1 and 2 illustrate anembodiment where the mixture including sand and shot are passed througha conditioner 57 prior to separation, an arrangement wherein the sandand shot mixture is passed through the air wash separator 61 prior topassing through a conditioner is contemplated by the present invention.

This latter case is preferable when it is desirable to condition thesand in the absence of shot.

The conditioner 57 includes an outer housing 63 which is cylindricallyshaped with a conical bottom 65. The side walls of the housing areradially spaced from a central axis. The passage 43 can serve as aninlet conduit 67 for the input of material to be conditioned. The inletconduit 67 is in the top portion of the housing 63. An outlet conduit 69is connected to the conical bottom 65 for the output of conditionedsand. The inlet conduit 67 and the outlet conduit 69 are coaxial withthe central axis of the housing 63. When in operation, the conditioner57 is placed so that the central axis is vertically aligned so that thematerial to be treated falls through the inlet conduit 67 and exits viathe outlet conduit 69.

A centrifugal throwing wheel 71 is disposed intermediate the inletconduit 67 and the outlet conduit 69. The throwing wheel 71 has an axisof rotation axially aligned and is disposed in the path of feed materialfalling through the inlet conduit 67. The feed material passing throughthe conduit 67 is projected radially outwardly by the throwing wheel 71.

The throwing wheel 71 includes a runnerhead with a plurality of radiallydirected vanes 77. A distribution head 73 is cone shaped with the baseof the cone contacting the central portion of the runnerhead 75 in thespace in the center of the throwing wheel 71 between the vanes 77.Preferably the runnerhead 75 and the vanes 77 are of a one piececonstruction and are preferably made of polyurethane. This constructionis illustrated in detail in FIGS. 9 and 10.

The runnerhead 75 is removably journaled on a spindle 79. The runnerhead75 has a square axially aligned opening which matches a similarly shapedend of the spindle 79 so as to provide a positive drive engagement. Thedistribution cone 73 is secured by bolting it in place to the end of thespindle 79. This attachment also serves to keep the throwing wheel 71 inplace.

The spindle 79 is axially aligned and mounted between spaced bearingsfor rotation. A pulley 81 at the lower end thereof is driven by anendless belt which is trained around another pulley 83 which isconnected to the shaft of a motor 85. The motor 85 is mounted exteriorto the housing 63 by a suitable bracket.

The feed material is projected radially outwardly from the axis ofrotation of the throwing wheel 71 so as to give a 360 coverage ofprojected particles. An impact surface 87 is radially spaced from theaxis of rotation of the throwing wheel 71. From a top view the impactsurface is circular in shape so that the thrown particles travel a givendistance before striking the impact surface 87.

The impact surface 87 has a cross section which is shaped like a tiltedU-shaped channel member. The impact surface 87 includes an impact plate89 which is directly in the path of the projected particles andangularlydisposed, preferably at about a 45 angle so as to direct theprojected particles upwardly after rebounding. A ricochet plate 91 isconnected to the impact plate at an angle, preferably at about a 90angle thereto, so as to deflect rebounding particles from the impactplate 89 toward the throwing wheel 71. A second ricochet plate 93 isconnected to and at about a 90 angle to the first ricochet plate 91. Thesecond ricochet plate 93 deflects particles downwardly toward the blaststream eminating from the centrifugal throwing wheel 71. This path isshown in FIG. 8 by a dotted line having arrows. The path is such thatthe collisions of the particles are maximized so that a scouring actionis achieved. The particles fall into the conical bottom 65 where theyexit via conduit 69.

The impact surface 87 is rigidly mounted in place to an inner wall 95.The inner wall 95 is concentric with the outer wall 63 so as to form aninner chamber 97 and an outer chamber 99.

According to the principles of the present invention, the particlesprojected from the throwing wheel 71 are immediately subjected to an airstream which flows through the projected and falling particles. The airstream flows through openings 101 in the top of the housing 63 andgenerally follows the solid lines with arrows as illustrated in FIG. 8.The air stream flows through the inner chamber 97 and downwardly throughthe projected particles and curves upwardly toward the outer chamber 99.The air stream is drawn through the outer chamber 99 by an outlet 103 orseveral outlets to evenly distribute the air flow which are connected toa low pressure source and a dust collector (not shown). The lighterparticles such as dust or fines which are airborne are drawn through theoutlet 103 and into the dust collector. The heavier particles continueto fall toward the bottom of the separator or to be projected againstthe impact surface 87. This arrangement results in a ricochetingparticle being subjected to the air stream immediately after leaving thethrowing wheel 71 prior to ricocheting and then again before fallinginto the conical bottom 65. Subjecting the particles to the air streamwhile in the free fall state effectively minimizes re-adherence ofcontaminants to the particles.

The conditioned sand passes through outlet conduit 69 into an elevator59 which carries the mixture to a separator 61. Advantageously, at leasta pair of separators 61 of the air wash type such as described andillustrated in US. Pat. No. 3,368,677 are utilized. In general, the airwash separator 61 subjects the falling mixture to a cross current ofair. A number of skimmer plates are provided in a separating chamber tofacilitate a separation of the mixture into individual streams inaccordance with their weight. In this respect the abrasive particles areheavier than the sand which, in turn, is heavier than the fines anddust. Thus, the abrasive particles fall or drop generally directlydownwardly into a discharge conduit 105 while the sand is diverted andreceived in another conduit 107. Fines, unusable sand grains and dustare conveyed through vents 109 to a dust collector (not shown).

It has been found that sand in the mixture fed to the separators is notalways of the desired size of fines and frequently is in smaller lumpswhich may be termed pea size. Generally, such pea-size lumps are about3/16 to A of an inch in diameter. Since this pea-size sand is heavierthan the fine grain sand, the pea-size sand will also go into theconduit with the abrasive particles which are large sized metal shot,thereby causing increased wear on the blast wheel vanes. Accordingly, itis necessary that this sand be separated from the abrasive particles ifthe sand recovery is to be maximized not for only reuse of the sand butfor reuse of the abrasive particles. Therefore, it is preferable toinclude a second air wash separator 62 in the system. Prior to feedingthe mixtures through the second air wash separator 62, the mixture ofabrasive particles and pea-size sand is fed through a pair of rollers111 which may be made of wear-resistant polyurethane. The closelypositioned rotating rollers 11 crush the pea-size sand into finegranular form for permitting the abrasive particles to retain theirnormal size. This mixture of crushed sand and abrasive particles is thenfed into the second separator 62. The second separator 62 collects theindividual streams of sand and abrasive particles distinct from eachother.

The substantially pure abrasive particles are received in hopper 35 forreuse by the abrasive blasting means 33. The sand passes through conduit107 to a magnetic drum separator 113 which removes the small quantity ofmetal abrasive that may be mixed with the otherwise substantially puresand. From the magnetic separator 113 the pure sand flows from an outlet115 and can be conveyed to a hopper for storage or directly to a sandmolding area for reuse.

In the embodiment of the present invention as illustrated in FIG. 12,sand is conditioned after it passes through the air wash separators 61and 62. In some cases, especially with green foundry sand, it isnecessary to recycle the sand several times through a conditioner 57 toobtain the desired organic level or clay content. To achieve this end,the sand from the outlet 115 of the apparatus illustrated in FIG. 1 canbe recycled through the conditioner 57. However, in many cases, the rateof sand flow will not allow this extra load on the conditioner 57 andseparators 61 and 62. If considerable recycling is required, the sandmay be fed into an auxiliary conditioning system generally indicated at121 in FIG. 11 and at 123 in FIG. 12.

The acceptable limits for conditioning sand vary with each foundry andare related to the type of sand involved, kind of binder, whether greenmolding sand is involved and the use being made of the sand. Claycontent of no-bake sand is generally not higher than approximately 2percent. However, green molding sand may contain 9-10 percent clay andwhen this is mixed relatively few conditioning cycles are needed toreduce the level of clay to the 2 percent level, but to reduce the claylevel to the 1 percent level, l20 reconditioning cycles may be required.Often several cycles are needed to reduce the organic residue remainingon the sand to the desired level.

In FIG. 11, the conditioning system 121 includes a plurality of stackedconditioners 57, each having mounted thereon a centrifugal throwingwheel 71 for projecting sand in a horizontal direction against an impactsurface 87. A single motor 122 mounted exterior to the conditionerdrives a plurality of throwing wheels 71. The uppermost conditioner 57has an outlet communicating with the inlet of the conditioner 57immediately below through passage 124. As illustrated in FIG. 11, onlytwo conditioners 57 are in stacked relationship, but it is contemplatedby the present invention that any number of conditioners 57 can bestacked depending on the degree of conditioning desired. The conditionedsand may be diverted from the lowermost or bottommost conditioner 57through an outlet passage 125 or can pass through conduit 155 into astorage area 157 by regulating a valve 169.

The sand reclamation system of FIG. 11 illustrates an embodiment ofthe'present invention wherein it is not necessary to subject the lumpsof molded sand to the action of projected abrasive particles. Thisembodiment is particularly useful if the sand is already in granulatedform or if the lumps of sand are broken easily by merely passing thesand through a conditioner 167 of the type hereinbefore described. Asillustrated in FIG. 11, the sand first passes through a conditioner 167and passes into a separator 129 by a conduit 127. If the sand is mostlygranulated, conditioner 167 is not needed and the sand can pass directlyto separator 129.

The separator 129 includes a wire mesh scalping drum 131 whichdistributes the feed mixture along the entire width of the hopper 133.The scalping drum 131 includes a spiral screw 135 which projectsinterior to and exterior to the wire mesh. The spiral screw 135 aids indistributing granulated particles along the length of the hopper 133while pushing the coarse scrap 137 out an open end of the drum 131.

The fine material which passes through the scalping drum 131 into thehopper 133 can be stored or conveyed into the conditioning system 121 bya conduit 159 which includes a valve 171. In operation, with valve 171closed a charge of sand accumulates in hopper 133. Valve 171 is openedto conveythe charge by a conduit 159 into the elevator 136 and thencethrough the conditioners 57. Valve 169 is adjusted so that theconditioned sand passes into conduit 155 and into storage hopper 157.With valve 165 of hopper 157 closed, the charge of sand accumulates inhopper 157. Preferably storage hopper 157 is at least the samecapacityof storage hopper 133. When substantially the entire charge hasbeen received in hopper 157 valve 165 is opened and the sand is recycledthrough the elevator 136 and conditioners 57 for a second pass. Byregulating valve 165 the number of passes of sand through theconditioners 57 can be carefully controlled so that the optimumconditioning of the sand is obtained;

When the sand has been sufficiently conditioned, valve 169 can beadjusted to divert the final pass of sand through conduit 125 and to astorage area or work area. Thus, the conditioning system 121 is ready toreceive a second charge of sand from hopper 133 which can be accumulatedwhile the first charge is being conditioned. The second charge isprocessed in a manner similar to the first charge.

FIG. 12 illustrates an embodiment of the present invention wherein theconditioners are stacked and driven by a single motor 141. The throwingwheels 71 of each conditioner 57 is mounted on a single shaft 143 whichis directly connected to the shaft of the motor 141.

The stacked conditioning system 123 of FIG. 12 includes a separatingsystem. The lower conditioner 57 includes an inner housing 145 having avent line 147 connected thereto. The inner housing 145 has a verticalwall substantially concentric with the wall of the outer housing 149.The inner housing 145 and the outer housing 149 are provided withbaffles 151 to provide a slow and smooth falling stream of material. Aconical conduit 153 is positioned below the inner housing 145 andincludes a portion concentric with and spaced from the inner housing145. As the sand falls over the flanged lip or lower baffle 151 of theinner housing 145, the fine particles of sand are drawn inwardly intothe conical conduit 153 by the suction maintained through the vent line147. The fine dust passes through the vent line while fines of apredetermined size are drawn into the conical conduit 153 and exit at anopening in the bottom thereof. Heavier particles fall downwardly to berecirculated or pass into a storage hopper.

It is contemplated that sand conditioners may be arranged in a varietyof ways to accommodate large quantities of sand. A plurality of stackedconditioners can communicate with a single elevator for processing sandor a plurality of stacked conditioning units can be arranged in serieswith various recycling means provided to provide fast, efficient andcomplete sand conditioning.

Preferred embodiments of this invention having been described andillustrated, it is to be realized that modifications thereof may be madewithout departing from the broad spirit and scope of the presentinvention as described in the appended claims.

What is claimed is:

1. Apparatus for granulating lumps of material comprising:

a. a drum supported for rotation about a substantially horizontal axis,said drum having an inner surface and a plurality of apertures forproviding passage ways for granulated material and abrasive particlestherethrough;

b. means for feeding lumps of material into an inlet end of said drum;

c. a spiral screw connected to the inner surface of said drum;

d. means for projecting a stream of abrasive particles with sufficientforce for granulating the lumps of material within the drum, saidprojecting means being positioned at an outlet end of said drum andabove the axis of rotation of said drum;

e. means for rotating said drum for moving the lumps of material againstthe force of the projecting stream of abrasive particles wherebygranulated material and spent abrasive particles pass through theapertures in said drum; and

pletely granulated. 2. Apparatus according to claim 1 wherein saidspiral screw has a uniform taper from the inlet end to the outlet end,said spiral screw being larger at the inlet end.

3. Apparatus according to claim 1 including a bar p0- sitioned withinsaid drum and substantially parallel to the axis of rotation of saiddrum for blocking the upward movement of material disposed within saiddrum.

1. Apparatus for granulating lumps of material comprising: a. a drumsupported for rotation about a substantially horizontal axis, said drumhaving an inner surface and a plurality of apertures for providingpassage ways for granulated material and abrasive particlestherethrough; b. means for feeding Lumps of material into an inlet endof said drum; c. a spiral screw connected to the inner surface of saiddrum; d. means for projecting a stream of abrasive particles withsufficient force for granulating the lumps of material within the drum,said projecting means being positioned at an outlet end of said drum andabove the axis of rotation of said drum; e. means for rotating said drumfor moving the lumps of material against the force of the projectingstream of abrasive particles whereby granulated material and spentabrasive particles pass through the apertures in said drum; and f. aseparator for removing the granulated material from the spent abrasiveparticles; g. said spiral screw including a first section near the inletend and a second section near the outlet end of said drum, said firstsection projecting into the interior of the drum a greater distance thansaid second section projects into the interior of the drum so that lumpsof molded sand tend to be pushed over said second section by the forceof abrasive particles and hled in said drum until completely granulated.2. Apparatus according to claim 1 wherein said spiral screw has auniform taper from the inlet end to the outlet end, said spiral screwbeing larger at the inlet end.
 3. Apparatus according to claim 1including a bar positioned within said drum and substantially parallelto the axis of rotation of said drum for blocking the upward movement ofmaterial disposed within said drum.